The employment of scrap thermoplastic resins in an extrusion process is a common method of efficiently and profitably recycling scrap resin. Typically, the scrap resin material is ground up and then fed into a screw-type extruder through a feed hopper, and often in admixture with a virgin resin material. By such recovery and recycle techniques, scrap-to-virgin resin ratios above to about 20% or higher have been reported; however and typically, the scrap-to-virgin resin ratios usually obtained have been up to about 10%, and more generally 5%.
One prime difficulty in the recycle of scrap polyethylene resin, or a similar resin, is that, on regrinding of the solid resin, the resin becomes a very low-density, fine particle-size, fluffy material. The reground resin is thus difficult to feed in a feed hopper in a continuous manner to an extruder, and, further, is difficult, by virtue of the difference in density, to admix properly with a granular virgin resin for a proper and continuous feed to an extruder. Thus, when the fluffy scrap resin, alone or with virgin resin, is attempted to be fed at high ratios into an extruder, quite often blockage of the feed hopper occurs, with the result that the extruder die is then starved for resin material. Such difficulties have often resulted in expensive down time for the extruder, while restricting the practical amount of the scrap resin to be employed in a recycling process to not more than about 5%. Thus, there exists a need for an apparatus and method by which thermoplastic scrap resin material, such as polyethylene, may be effectively and efficiently employed in an extruder at high ratios, without the difficulties occasioned by the prior art.